A. Field of the Invention
The present invention relates generally to the optical communications or telecommunications field, and, more particularly to an electrical circuit pack ejector system that provides a preemptive warning to the circuit pack.
B. Description of the Related Art
Electrical circuit packs or circuit packs include a circuit board with components mounted thereon and a connector on one edge of the board. In a typical interconnection scheme, a plurality of pins is provided through a backplane mounted at the far end of a shelf. Each pack is inserted vertically or horizontally into the shelf (also known as a “subrack”) on guideways so that the connector engages the appropriate pins for connection to that circuit pack when the circuit pack is in its final position. The circuit pack is usually inserted into the backplane using a lever, sometimes referred to as a latch, injector-ejector, or circuit pack ejector system.
Historically, most telecommunication equipment requires the physical shut down (powering off) of the entire system prior to servicing an individual circuit pack. For this reason, most commercially-available circuit pack ejector systems do not require or include a mechanism for detecting the activation of an ejector arm and subsequent circuit pack ejection. However, modern telecommunications equipment vendors now offer “hot-swappable” circuit packs that allow an individual circuit pack to be serviced without disabling other adjacent operating circuit packs. In addition, some systems require “hitless” removal of circuit packs, where removal of a circuit pack does not affect data traffic on other circuit packs in the system. To accomplish this, the logic on the circuit pack needs to be shutdown prior to circuit pack removal, which requires advanced notification that removal is going to occur. Without this advanced notification, signals may be transitioning on the circuit pack backplane when removal occurs, adversely affecting data on other circuit packs in the system.
To combat the issue, some vendors now offer “intelligent” ejector systems with an integrated mechanism providing an advanced warning to the system that a circuit pack is being removed for service. Some examples of such ejector systems include the Ripac CompactPCI injector/extractor handle available from Rittal Corporation of Springfield, Ohio, and the CPCI handles available from Elma Electronic, Inc. of Fremont, Calif.
Unfortunately, currently available “intelligent” ejector systems use a mechanical switch to provide preemptive circuit pack ejection feedback. Such mechanical-based ejector systems suffer from several drawbacks. First, such systems are expensive due to the number of components in such ejector systems, and the assembly time required for such systems. Second, existing ejector systems use springs, levels, and other mechanical contacts as a switch mechanism, which are susceptible to damage and wear.
Third, mechanical-type switches require additional circuitry on the circuit pack to “debounce” the switch mechanism. When a mechanical switch closes, the switch contacts do not instantly and finally close. Rather, the contacts close and then bounce open. This cycle repeats for a period of time, depending upon the switch-manufacturing technology. Thus, mechanical switches need additional circuitry to “debounce” the switch and accommodate for this situation. This additional circuitry prevents microscopic switch contact chatter from generating a false positive on or off condition.
Finally, mechanical-based ejector systems require cut-outs or openings in circuit pack faceplates typically for sensor switches, plungers, optical windows, etc. Such faceplate openings are sources of electromagnetic interference (“EMI”) since a circuit pack faceplate is part of a Faraday cage or conductive case shield that protects the circuit pack components within from EMI. The strength and frequency of the EMI passing through the faceplate openings is a function of three variables: the size of the opening, depth of the opening, and the strength of the source of the EMI.
Thus there is a need in the art for an electrical circuit pack ejector system that provides a preemptive warning to the circuit pack and overcomes the problems of the related art.